Many agricultural combines or harvesters utilize a rotary threshing and separating system to loosen and separate crop material (e.g. grain, straw, legumes, and the like) from crop residue and waste (e.g. husks, cobs, pods, and the like). The threshing system typically includes a rotor drivingly rotated inside a threshing chamber. The rotor often includes a frusto-conical inlet end with a helical flight or flights for conveying crop material into the threshing chamber. In addition, the rotor typically includes a plurality of elements that project outwardly from the main body of the rotor. These projections can include rasp bars or other protrusions designed to convey a mat of crop material along a helical path through the threshing chamber as the rotor rotates. The rasp bars can engage inner surfaces of the threshing chamber to separate crop residue from crop material. Some examples of rotors used in threshing and separating systems are described in U.S. Pat. No. 8,636,568 and U.S. Pat. No. 8,636,569, both assigned to the applicant, the contents of both being incorporated by reference herein in their entireties.
Many threshing chambers include one or more transport vanes that assist in guiding the crop material and residue from the inlet or “front” of the threshing chamber to the opposite end or “rear” of the threshing chamber. The positioning and orientation of vanes can be adjusted, depending on the crop and other variables, to control the rate of flow of material through the threshing chamber, and consequently, the dwelling time of crop material in the threshing system. For example, vanes can be adjusted to increase the rate at which crop material moves rearward per each revolution of the rotor. Some examples of crop transport vanes are described in U.S. Pat. No. 8,926,415, assigned to the applicant, the content of which is incorporated by reference herein in its entirety.
Although vanes assist in guiding crop material toward the rear of the threshing chamber, vanes also create resistance forces that make it more difficult to advance crop material through the chamber. As crop material accumulates in the threshing space, and rubs against the vanes, more horsepower is required to move the crop material through the chamber. This reduces the efficiency of the threshing process, due to a higher fuel consumption and increased energy cost.
Transport vanes can also be problematic when the flow rate of crop material through the cage needs adjustment. Some transport vanes are limited in how precisely they can control crop flow rate. For example, some vanes can only be positioned in one of three settings, corresponding to a “fast” speed, “medium” speed and “slow” speed. This can be undesirable for crop conditions that require finer adjustments or a variety of different speeds.
Based on the foregoing reasons, there is a need for improved threshing and separating systems that address multiple objectives, including but not limited to increased energy efficiency and better control over crop flow through the threshing and separating system.